迷宫问题|深度优先搜索&广度优先搜索

什么样的数据结构决定了什么样的方法。

1.用栈实现深度优先搜索（DSF）

 #include <stdio.h>

 #define MAX_ROW 5
 #define MAX_COL 5

 struct point { int row, col; } stack[512];
 int top = 0;

 void push(struct point p)
 {
     stack[top++] = p;
 }

 struct point pop(void)
 {
     return stack[--top];
 }

 int is_empty(void)
 {
     return top == 0;
 }

 int maze[MAX_ROW][MAX_COL] = {
     0, 1, 0, 0, 0,
     0, 1, 0, 1, 0,
     0, 0, 0, 0, 0,
     0, 1, 1, 1, 0,
     0, 0, 0, 1, 0,
 };

 void print_maze(void)
 {
     int i, j;
     for (i = 0; i < MAX_ROW; i++) {
         for (j = 0; j < MAX_COL; j++)
             printf("%d ", maze[i][j]);
         putchar('\n');
     }
     printf("*********\n");
 }

 struct point predecessor[MAX_ROW][MAX_COL] = {
     {{-1,-1}, {-1,-1}, {-1,-1}, {-1,-1}, {-1,-1}},
     {{-1,-1}, {-1,-1}, {-1,-1}, {-1,-1}, {-1,-1}},
     {{-1,-1}, {-1,-1}, {-1,-1}, {-1,-1}, {-1,-1}},
     {{-1,-1}, {-1,-1}, {-1,-1}, {-1,-1}, {-1,-1}},
     {{-1,-1}, {-1,-1}, {-1,-1}, {-1,-1}, {-1,-1}},
 };

 void visit(int row, int col, struct point pre)
 {
     struct point visit_point = { row, col };
     maze[row][col] = 2;
     predecessor[row][col] = pre;
     push(visit_point);
 }

 int main(void)
 {
     struct point p = { 0, 0 };

     maze[p.row][p.col] = 2;
     push(p);

     while (!is_empty()) {
         p = pop();
         if (p.row == MAX_ROW - 1  /* goal */
             && p.col == MAX_COL - 1)
             break;
         if (p.col+1 < MAX_COL     /* right */
             && maze[p.row][p.col+1] == 0)
             visit(p.row, p.col+1, p);
         if (p.row+1 < MAX_ROW     /* down */
             && maze[p.row+1][p.col] == 0)
             visit(p.row+1, p.col, p);
         if (p.col-1 >= 0          /* left */
             && maze[p.row][p.col-1] == 0)
             visit(p.row, p.col-1, p);
         if (p.row-1 >= 0          /* up */
             && maze[p.row-1][p.col] == 0)
             visit(p.row-1, p.col, p);
         print_maze();
     }
     if (p.row == MAX_ROW - 1 && p.col == MAX_COL - 1) {
         printf("(%d, %d)\n", p.row, p.col);
         while (predecessor[p.row][p.col].row != -1) {
             p = predecessor[p.row][p.col];
             printf("(%d, %d)\n", p.row, p.col);
         }
     } else
         printf("No path!\n");

     return 0;
 }

2.用队列实现广度优先搜索

 #include <stdio.h>

 #define MAX_ROW 5
 #define MAX_COL 5

 struct point {
     int row, col, predecessor;
 } queue[512];
 int head = 0, tail = 0;

 void enqueue(struct point p) {
     queue[tail++] = p;
 }

 struct point dequeue(void) {
     return queue[head++];
 }

 int is_empty(void) {
     return head == tail;
 }

 int maze[MAX_ROW][MAX_COL] = { 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0,
         1, 1, 1, 0, 0, 0, 0, 1, 0, };

 void print_maze(void) {
     int i, j;
     for (i = 0; i < MAX_ROW; i++) {
         for (j = 0; j < MAX_COL; j++)
             printf("%d ", maze[i][j]);
         putchar('\n');
     }
     printf("*********\n");
 }

 void visit(int row, int col) {
     struct point visit_point = { row, col, head - 1 };
     maze[row][col] = 2;
     enqueue(visit_point);
 }

 int main(void) {
     struct point p = { 0, 0, -1 };

     maze[p.row][p.col] = 2;
     enqueue(p);

     while (!is_empty()) {
         p = dequeue();
         if (p.row == MAX_ROW - 1 /* goal */
                 && p.col == MAX_COL - 1)
             break;
         if (p.col + 1 < MAX_COL /* right */
                 && maze[p.row][p.col + 1] == 0)
             visit(p.row, p.col + 1);
         if (p.row + 1 < MAX_ROW /* down */
                 && maze[p.row + 1][p.col] == 0)
             visit(p.row + 1, p.col);
         if (p.col - 1 >= 0 /* left */
                 && maze[p.row][p.col - 1] == 0)
             visit(p.row, p.col - 1);
         if (p.row - 1 >= 0 /* up */
                 && maze[p.row - 1][p.col] == 0)
             visit(p.row - 1, p.col);
         print_maze();
     }
     if (p.row == MAX_ROW - 1 && p.col == MAX_COL - 1) {
         printf("(%d, %d)\n", p.row, p.col);
         while (p.predecessor != -1) {
             p = queue[p.predecessor];
             printf("(%d, %d)\n", p.row, p.col);
         }
     } else
         printf("No path!\n");

     return 0;
 }

当然，还可以优化。